ROOT is an object oriented histogramming package developed by CERN to replace earlier packages. ROOT is written in C++, on an ad hoc platform that provides a graphical user interface, container classes, reflection, and a command line interpreter (CINT). In addition to histogramming, ROOT provides other data analysis functions such as curve fitting by regression analysis.
A key feature of ROOT is its data abstraction model, but it is one that can be confusing to new users. A tree, and its substructures (branches and leaves), can be seen as a sliding window to the raw data, as stored in a file. Data from the next entry in the file can be retrieved by advancing the index in the tree. This avoids memory allocation issues associated with object creation, and allows the tree to act as a lightweight container while handling buffering invisibly.
ROOT is used extensively in data acquisition and analysis in high energy physics experiments.
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